24. Specifying the tooltip to be displayed for a given element.

Extension property tooltip-content allows to specify the textual contents of a tooltip (also called "balloon help" or "mouse hover"). This tooltip is displayed by XXE when the user moves the mouse over the view of the element which is the subject of the CSS rule containing tooltip-content.

The value of this property is any generated content which evaluates as text. A generated content which does not evaluate as text is simply ignored.

This property is not inherited and cannot be inherited by specifying keyword inherit.


pre.tooltip {
    tooltip-content: "<html>1<body><tt>pre=<big>" element-local-name()¬
"</big></tt><br><small>(HTML tooltip)</small>";

pre.tooltip b {
    tooltip-content: "b/@lang=" attr(lang);

pre.tooltip i {
    tooltip-content: "i inside \A "2 xpath("local-name(parent::*)");

pre.tooltip u {
    tooltip-content: "u is not a " icon(left-link)3 "link";


A value which starts with "<html>" is parsed as HTML 3.2 and allows to specify a tooltip containing “rich text”.


A value may contain newline characters ("\A ").


Generated content icon(left-link), which evaluates as an image, is silently skipped.